AngularJS Q1

Explain what are directives ? Mention some of the most commonly used directives in AngularJS application ?

A directive is something that introduces new syntax, they are like markers on DOM element which attaches a special behavior to it. In any AngularJS application, directives are the most important components. Some of the commonly used directives are ng-model, ng-App, ng-bind, ng-repeat , ng-show etc.

Explain what is injector?

An injector is a service locator. It is used to retrieve object instances as defined by provider, instantiate types, invoke methods and load modules. There is a single injector per Angular application, it helps to look up an object instance by its name.

Explain what Angular JS routes does

Angular js routes enable you to create different URLs for different content in your application. Different URLs for different content enables user to bookmark URLs to specific content. Each such bookmarkable URL in AngularJS is called a route A value in Angular JS is a simple object. It can be a number, string or JavaScript object. Values are typically used as configuration injected into factories, services or controllers. A value should be belong to an AngularJS module. Injecting a value into an AngularJS controller function is done by adding a parameter with the same name as the value

Explain what is the difference between AngularJS and backbone.js?

AngularJS combines the functionalities of most of the 3rd party libraries, it supports individual functionalities required to develop HTML5 Apps. While Backbone.js do their jobs individually.

Explain what is data binding in AngularJS

Automatic synchronization of data between the model and view components is referred as data binding in AngularJS. There are two ways for data binding Data mining in classical template systems Data binding in angular templates

Explain what is DI (Dependency Injection ) and how an object or function can get a hold of its dependencies ?

DI or Dependency Injection is a software design pattern that deals with how code gets hold of its dependencies. In order to retrieve elements of the application which is required to be configured when module gets loaded , the operation "config" uses dependency injection. These are the ways that object uses to hold of its dependencies Typically using the new operator, dependency can be created By referring to a global variable, dependency can be looked up Dependency can be passed into where it is required

Explain what is directive and Mention what are the different types of Directive?

During compilation process when specific HTML constructs are encountered a behaviour or function is triggered, this function is referred as directive. It is executed when the compiler encounters it in the DOM. Different types of directives are Element directives Attribute directives CSS class directives Comment directives

Explain the concept of scope hierarchy? How many scope can an application have?

Each angular application consist of one root scope but may have several child scopes. As child controllers and some directives create new child scopes, application can have multiple scopes. When new scopes are formed or created they are added as a children of their parent scope. Similar to DOM, they also creates a hierarchical structure.

Explain what is factory method in AngularJS?

For creating the directive, factory method is used. It is invoked only once, when compiler matches the directive for the first time. By using $injector.invoke the factory method is invoked.

Explain what is string interpolation in Angular.js ?

In Angular.js the compiler during the compilation process matches text and attributes using interpolate service to see if they contains embedded expressions. As part of normal digest cycle these expressions are updated and registered as watches.

Explain what is services in AngularJS

In AngularJS services are the singleton objects or functions that are used for carrying out specific tasks. It holds some business logic and these function can be called as controllers, directive, filters and so on.

Who created Angular JS ?

Intially it was developed by Misko Hevery and Adam Abrons. Currently it is being developed by Google

Explain what is Angular Expression? Explain what is key difference between angular expressions and JavaScript expressions?

Like JavaScript, Angular expressions are code snippets that are usually placed in binding such as {{ expression }} The key difference between the JavaScript expressions and Angular expressions Context : In Angular, the expressions are evaluated against a scope object, while the Javascript expressions are evaluated against the global window Forgiving: In Angular expression evaluation is forgiving to null and undefined, while in Javascript undefined properties generates TypeError or ReferenceError No Control Flow Statements: Loops, conditionals or exceptions cannot be used in an angular expression Filters: To format data before displaying it you can use filters

Explain what is linking function and type of linking function?

Link combines the directives with a scope and produce a live view. For registering DOM listeners as well as updating the DOM, link function is responsible. After the template is cloned it is executed. Pre-linking function: Pre-linking function is executed before the child elements are linked. It is not considered as the safe way for DOM transformation. Post linking function: Post linking function is executed after the child elements are linked. It is safe to do DOM transformation by post-linking function

Explain what is scope in AngularJS

Scope refers to the application model, it acts like glue between application controller and the view. Scopes are arranged in hierarchical structure and impersonate the DOM ( Document Object Model) structure of the application. It can watch expressions and propagate events.

Mention what are the characteristics of "Scope"?

To observer model mutations scopes provide APIs ($watch) To propagate any model changes through the system into the view from outside of the Angular realm A scope inherits properties from its parent scope, while providing access to shared model properties, scopes can be nested to isolate application components Scope provides context against which expressions are evaluated

With options on page load how you can initialize a select box

You can initialize a select box with options on page load by using ng-init directive

Mention what are the styling form that ngModel adds to CSS classes ?

ngModel adds these CSS classes to allow styling of form as well as control ng- valid ng- invalid ng-pristine ng-dirty